Patient-position-monitoring method and system for use during medical diagnostic and therapeutic procedures

ABSTRACT

A light beam is directed upon a retroreflective element, located adjacent the pertinent portion of the patient&#39;&#39;s body and is reflected upon a photocell or some other photoresponsive means. If there is any appreciable change in the patient&#39;&#39;s position, the signal from the photocell will change. The changed signal can be employed to perform a control function, such as actuating a warning device, or terminating the diagnostic or therapeutic procedure, so that the radiation will not be misdirected. The light beam is preferably produced by an optical system comprising a lamp, an apertured member to produce a small spot of light, a partially light-transmitting mirror, and a lens for focusing the beam upon the retroreflective element. The reflected beam is preferably focused by the lens through the mirror and upon the photocell. The retroreflective element is preferably in the form of a small piece of retroreflective adhesive tape, to be stuck to or adjacent to the patient&#39;&#39;s body.

United States Patent [72] Inventor Glen Sandberg OTHER REFERENCES [2'] AI N g g-2 Willis, 0. R.; IBM Technical Disclosure Bulletin; Vol. 6,

l No 6;Nov., I963; .13; 250- 22l. [22] Filed Apr. 16, 1910 W I [45]Patented Dec. 21, 1971 Primary Examiner-Anthony L. Blrch [73] AssigneeMichael Reese Hospital and Medical Center y L Goldsmith, Clement & rd n[54] PAT]ENT-POSITION-MONITORING METHOD ABSTRACT: A light beam isdirected upon a retroreflective AND SYSTEM FOR USE DURING MEDICALelement, located adjacent the pertinent portion of the pa- DIAGNOSTICAND THERAPEUTIC PROCEDURES tient's body and is reflected upon aphotocell or some other 21 Claims, 3 Drawing Figs. photoresponsivemeans. If there is any appreciable change in the patients position, thesignal from the photocell will Cl g g change. The changed signal can beemployed to perform a H i I t Cl cdsbfllm control function, such asactuating a warning device. or ter- 'L' 250/65 93 minating thediagnostic or therapeutic procedure. so that the 95 I03 2 radiation willnot be misdirected. The light beam is preferably A 5 produced by anoptical system comprising a lamp an apertured member to produce a smallspot of light, a partially light- 5 References Cited transmittingmirror, and a lens for focusing the beam upon the UNITED STATES PATENTSretroreflective element. The reflected beam is preferably focused by thelens through the mirror and upon the 22 3 32; g g 250/221) photocell.The retrorefiective element is preferably in the ig g i g gSO/ZH form ofa small piece of retroreflective adhesive tape, to be 2, art eta. 25/221X stuck to oradjacemto the patients body 42 X- RAY TUBE WARNmGDEVICE RELAY AMPUF! El? FIG PHOT O CELL PATENTEU B 2 I971 MS mmy W m 1wNd /v f v uw Mn PATIENT-POSITION-MONITORING METHOD AND SYSTEM FOR USEDURING MEDICAL DIAGNOSTIC AND THERAPEUTIC PROCEDURES This inventionrelates to a method and system for indicating any appreciable change inthe position of a patient during medical procedures utilizing ahigh-energy beam source such as radiography, radioisotope or ultrasonicscanning, radiation therapy, laser beam treatment or the like, orutilizing a highenergy source. Any change in the position of the patientis undesirable, because such change may cause the high-energy beam orradiation to be misdirected, or because inaccurate sensing of thehigh-energy source may give false data.

A misdirected radiation therapy beam may have serious effects on theintended cure of the patient. All high-energy beams such as radiationbeams must be considered as potentially harmful, even at levels used indiagnostic procedures, and a misdirected diagnostic beam will usuallynecessitate a repeat procedure. By reducing the number of these repeats,the system will achieve the goal of reducing unnecessary exposure ofpatients in diagnostic procedures utilizing X-rays or radioactiveisotopes, as well as in therapy procedures.

The method and system of the present invention may be employed toperform a control function, such as producing a warning signal, orshutting off the source of radiation or source of other high-energybeam. In either case, the operator will reposition the patient beforecontinuing the procedure.

It is an object of the present invention to produce a monitoring systemwhich is reliable and highly effective, and easy to use in the presenceof normal room light.

Thus, the present invention preferably involves directing a light beamupon a retroreflective element, associated with, mounted on, or adjacentthe pertinent portion of the patients body. The light beam is reflectedupon a photocell or some other photoresponsive means. If there is anyappreciable movement of the patients body, the signal from the photocellor other photoresponsive means will be changed, or will otherwiseindicate the change of position or movement. Such signal is preferablyfed through an amplifier to a relay which can actuate a warning device,and can also, if desired, control or turn off the X-ray tube or anyother source of radiation or high energy.

The retroreflective element is preferably in the form of a small pieceof retroreflective adhesive tape or other similar sheet material. Inthis way, the retroreflective element can easily be applied to apertinent portion of the patients body.

The light source preferably comprises a lamp, an apertured member toproduce a small spot of light from the lamp, and an optical system forfocusing the beam upon the retroreflective element. Such an opticalsystem preferably comprises a partially light-transmissive mirror and alens. The reflected beam is preferably focused by the same lens, throughthe mirror and upon the photocell.

The signal from the photocell is preferably fed through an amplifier toa relay which may perform various control functions, such as actuating awarning device or turning off the source of radiation, or both.

Further objects, advantages and features of the present invention willappear from the following description, taken with the accompanyingdrawings, in which:

FIG. 1 is a diagrammatic elevation of a patient-positionmonitoringsystem, to be described as an-illustrative embodiment of the presentinvention.

FIG. 2 is an elevational view, partially in section of the opticalsystem of FIG. 1.

FIG. 3 is a block diagram of the electrical system of FIG. 1.

As shown in FIG. I, the invention is embodied in a monitoring system 10,comprising a retroreflective element 12, mounted on the pertinentportion of the patients body 14. Preferably, the retroreflective elementI2 takes the form of a small piece of retroreflective tape or othersheet material, with adhesive material on the back side thereof, so thatthe element 12 can easily be stuck to the patient's body. The adhesivematerial is preferably of the pressure sensitive, permanently tackytape.

The retroreflective element 12 is preferably applied to the patientsbody at or near the site of the patients exposure to radiation. If thepatient is immobilized, then the element I2 may be applied to the tableor couch to which the patient is fixed. The size of the retroreflectiveelement is chosen according to the required tolerance for displacementof the patient. Thus, any movement of the retroreflective element out ofthe light beam will indicate that the irradiated portion of the patientsbody has moved more than a prescribed amount.

A light beam 16 is projected upon the retroreflective element l2 and isreflected back by the element. The material of which the retroreflectiveelement is made has the characteristic that any impinging light beam isreflected directly back, along its path of impingement, even if thesurface is not normal to the path of impingement of the light beam. Sucha material is available from the 3M Company and has been used for makingreflective highway signs and the like.

A retroreflective target with the coaxial light source and detectordescribed herein achieves a high contrast between the target and thebackground in the presence of normally encountered ambient light.

The light beam is produced and is also utilized by an optical unit 18,shown in section in FIG. 2. The light is produced by a lamp 20 and isdirected through a small aperture 22 in a plate 24 or the like. Ineffect, a small spot of light is produced at the aperture 22. The lamp20 is mounted in a housing 26.

The small spot of light is projected upon the retroreflective element 12by a mirror 28 and a lens 30, mounted in a tubular housing 32. Themirror 28 is at an oblique angle to the optical axis of the lens 30, sothat the lamp 20 and the apertured plate 24 can be disposed laterallyfrom the axis of the lens. As shown, the light beam is reflected at anangle of about by the mirror 28. The lens 30 focuses the light beam soas to produce an image of the small spot of light, on theretroreflective element 12. Although a lens such as that illustrated inthe drawings will function satisfactorily, an axicon lens system willperform in a superior manner in this application. Axicon lenses aredescribed in U.S. Pat. No. 2,759,393, and are used in coaxiallight-emitting systems. In the present invention and axicon lensachieves a sharp focus over an extended distance to enhance the utilityof the system.

The light beam is reflected back through the lens 30 by the element 12and is focused upon photoresponsive means, illustrated as comprising aphotosensitive device such as photocell 34, disposed behind the mirror28. While the mirror could be apertured, it is preferably of the typehaving a reflective coating which is partially light-transmissive. Thus,the reflected beam is able to pass through the mirror to the photocell34. It will be understood that the photocell 34 may be of any suitabletype, such as a solid state photodiode.

The reflective element I2 is of small size so that any appreciable ormedically significant movement by the patient will move the element 12out of the path of impingement of light beam 16, hence will cause achange in the amount of light reflected to the photocell 34. That isbecause the retroreflective element will be moved out of the path of thebeam of light and thus the light beam will not be reflected back to thephotocell. As such, the electrical signal produced by the photocell 34will exhibit a corresponding change.

As shown in FIG. 3, the output signal from the photocell is preferablyfed into an amplifier 36 which produces a corresponding amplifiedoutput, adapted to operate a control relay 38 or the like. The controlrelay 38 may be arranged to perform various control function, such asactuating a warning device 40, when the reflected light beam isdiminished in magnitude by movement of the patient. The control relay 38may also be arranged to shut off or deactivate the radiation source,shown as an X-ray tube 42. It will be understood that the radiationsource may comprise any other suitable means for producing radiation,such as an atomic irradiator utilizing radioactive cobalt, for example,or may comprise other means for producing a high-energy beam, such as alaser beam, for example.

The optical unit 18 may have a swivel mounting bracket 44 which providesfor universal adjustment, so that the light beam can easily be aimed atthe retroreflective element '12. The bracket 44 is secured to a wall 46or any other suitable support. in some cases, the optical unit may bemounted on the carriage which supports the X-ray tube 42. The unit mayalso be mounted rigidly in the room or affixed to the equipment to serveas a pointer for positioning the patient.

In the operation of the patient position monitoring system, theretroreflective element 12 is mounted on the patients body, at or nearthe intended siteof the diagnostic procedure or therapy. When thepatient has been properly positioned, the light beam 16 is aimed so thatit falls directly upon the retroreflective element 12. The medicalprocedure is then commenced.

If the patient moves appreciably, the reflected light, projected uponthe photocell 34, diminishes. The resulting signal produced by thephotocell may be amplified by amplifier 36, and is employed to actuatethe warning device 40, and also preferably to deactivate the X-ray tube42 or other high-energy beam source. The warning device 40 may comprisea buzzer, bell, lamp or the like. In response to the warning, theoperator repositions the patient so that the procedure can be completed.

The monitoring system is applicable to certain types of diagnosticX-rays, to X-ray therapy, and to other radiation and high-energy sourcetherapy and diagnostic procedures. Thus, the high-energy source may be aremote beam source, or, for example, a radioactive source administeredto the patient, the emission of which is scanned and detected externallyof the patient in a known manner. Indeed the system may utilize the eyeas the retroreflective element in certain diagnostic and therapeuticprocedures.

it will be recognized that the patient position monitoring system ishighly reliable and effective, yet is easy to use.

Various modification, alternatives and equivalents can be employed.Thus, for example, it is possible to interchange the positions of thephotocell 34 and the lamp 2.0, with its apertured plate 24. Further aconcave mirror or mirrors may be used for focusing the emitted andreflected light beams, instead of a lens or lenses.

Also, for example, a continuous laser or a light emitting diode can beused for the light beam source. Such a diode is essentially a pointsource of light, which can be focused by means of a lens upon theretroreflective element. An optical system is used in connection withthe laser, to form a narrow Y beam of light. The retroreflective elementmay comprise a corner reflector of mirrors, prisms or transparentjewels,to be attached to the patients body.

What is claimed is:

1. In combination with a radiation source to be used with a patient in amedical therapeutic or diagnostic procedure, apatient-position-monitoring system comprising a retroreflective elementadjacent the pertinent portion of the patients body, a remote source fordirecting a beam of light upon said retroreflective element, said lightbeam being reflected by said element, photoresponsive means for remotelyreceiving the reflected light beam from said element to develop a signalindicative of any medically significant change in the position of thepatient, and means responsive to said signal for signalling said changein position.

2. A system according to claim 1, in which said retroreflective elementcomprises a piece of retroreflective material having an adhesive backingfor securing said material to the pertinent portion of the patientsbody.

3. A system according to claim 1, in which said light beam sourceincludes a lamp, an apertured member restricting the light from saidlamp to a small spot, and means for focusing said small spot upon saidretroreflective element.

4. A system according to claim 1, in which said light beam sourcecomprises a laser beam source.

5. A system according to claim 1, in which said light beam sourceincludes a light-emitting diode, and means for focusing the light beamfrom said diode on the retroreflective element.

6. A system according to claim 3, in which said focusing means comprisesa mirror and a lens, said mirror being disposed at an oblique angle tothe optical axis of said lens.

7. A system according to claim 6, in which said photoresponsive meanscomprising a photosensitive device disposed behind said mirror, saidmirror being partially lighttransmissive, the reflected light beam beingadapted to be focused by said lens, through said mirror and upon saidphotosensitive device.

8. A system according to claim I, in which said light beam sourceincludes means for developing a small spot of light, and a partiallylight-transmissive mirror and a lens for projecting said spot upon saidretroreflective element, the reflected light beam being adapted to beprojected upon said photoresponsive means through the agency of saidlens and said mirror.

9. In the combination of claim 1 in which said radiation source remotelyproduces a radiant energy beam directed toward the patient, and saidmeans responsive to said signal controls said radiation source.

10. in the combination of claim 9, wherein said controlling means isadapted to deactivate said radiation source.

11. in the combination of claim 9, wherein the retroreflective elementis secured to the patient.

12. A system according to claim 9, in which said light beam sourceincludes means for developing a small spot of light, and a partiallylight-transmissive mirror and a lens for projecting said spot upon saidretroreflective element, the reflected spot of light being adapted to beprojected upon said photoresponsive means through the agency of saidlens and said mirror.

13. In the combination of claim 12 in which said lens is an axicon lens.

14. A patient position monitoring system for use during a medicalprocedure involving the exposure of a patient to radiation and forcontrolling a radiation source comprising: a radiation source, aretroreflective element to be mounted closely adjacent the pertinentportion of the patients body to be exposed to said radiation, a lightsource for directing a beam of light upon the retroreflective element,said light beam being reflected by said element, photoresponsive meansfor receiving the reflected light beam from said retroreflective elementto develop a signal indicative of any substantial change in the positionof the patient from a first position, and means connected between saidphotoresponsive means and said radiation source and operative todeactivate said radiation source in response to a change in the signalfrom said photoresponsive means.

15. A method of sensing medically significant changes in the position ofa patient during a medical radiant energy exposure procedure, comprisingthe steps of mounting a retroreflective element adjacent the patientsbody, remotely directing a beam of light upon the retroreflectiveelement, and remotely directing the resulting reflected light beam fromthe retroreflective element.

[6. A method according to claim 15, comprising the further step ofperforming a control function in response to a change in the reflectedlight beam.

17. A method according to claim 15, comprising the further step ofproducing a warning signal in response to a change in the reflectedlight beam.

18. A method according to claim 15, comprising the further step ofdiscontinuing the medical procedure in response to a change in thereflected light beam.

19. A method of responding to a medically significant change of positionof a patient during a medical procedure comprising the steps ofproviding a retroreflective element in a fixed relation adjacent thepertinent portion of the pateints body, directing a beam of light from aremote position toward the retroreflective element, remotely detectingthe reflected beam of light from said retroreflective element, producinga warning signal in response to a medically significant change ofposition of the patient from a first position to another position, anddiscontinuing the medical procedure in response to said warning signal.

20. A method according to claim 19, comprising the further steps ofbeaming radiant energy toward the patient, and

discontinuing said beaming in response to the signal.

21. A method according to claim 20 in which the retroreflective elementis mounted on the patient. 5

t i i i t UNITED STATES PATENT oTFTeE CERTIFICATE OF CORRECTION PatentNo. 3 62Q,594 Dated December 21, 1971 Inventor(s) Glen Sandberg It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 4, Claim 19, line 66, "pateint's" should be patient's Column 5,Claim 21, line l, "20" should be *9 19 Signed and sealed this 31st dayof October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. In combination with a radiation source to be used with a patient in amedical therapeutic or diagnostic procedure, apatient-position-monitoring system comprising a retroreflective elementadjacent the pertinent portion of the patient''s body, a remote sourcefor directing a beam of light upon said retroreflective element, saidlight beam being reflected by said element, photoresponsive means forremotely receiving the reflected light beam from said element to developa signal indicative of any medically significant change in the positionof the patient, and means responsive to said signal for signalling saidchange in position.
 2. A system according to claim 1, in which saidretroreflective element comprises a piece of retroreflective materialhaving an adhesive backing for securing said material to the pertinentportion of the patient''s body.
 3. A system according to claim 1, inwhich said light beam source includes a lamp, an apertured memberrestricting the light from said lamp to a small spot, and means forfocusing said small spot upon said retroreflective element.
 4. A systemaccording to claim 1, in which said light beam source comprises a laserbeam source.
 5. A system according to claim 1, in which said light beamsource includes a light-emitting diode, and means for focusing the lightbeam from said diode on the retroreflective element.
 6. A systemaccording to claim 3, in which said focusing means comprises a mirrorand a lens, said mirror being disposed at an oblique angle to theoptical axis of said lens.
 7. A system according to claim 6, in whichsaid photoresponsive means comprising a photosensitive device disposedbehind said mirror, said mirror being partially light-transmissive, thereflected light beam being adapted to be focused by said lens, throughsaid mirror and upon said photosensitive device.
 8. A system accordingto claim 1, in which said light beam source includes means fordeveloping a small spot of light, and a partially light-transmissivemirror and a lens for projecting said spot upon said retroreflectiveelement, the reflected light beam being adapted to be projected uponsaid photoresponsive means through the agency of said lens and saidmirror.
 9. In the combination of claim 1 in which said radiation sourceremotely produces a radiant energy beam directed toward the patient, andsaid means responsive to said signal controls said radiation source. 10.In the combination of claim 9, wherein said controlling means is adaptedto deactivate said radiation source.
 11. In the combination of claim 9,wherein the retroreflective element is secured to the patient.
 12. Asystem according to claim 9, in which said light beam source includesmeans for developing a small spot of light, and a partiallylight-transmissive mirror and a lens for projecting said spot upon saidretroreflective element, the reflected spot of light being adapted to beprojected upon said photoresponsive means through the ageNcy of saidlens and said mirror.
 13. In the combination of claim 12 in which saidlens is an axicon lens.
 14. A patient position monitoring system for useduring a medical procedure involving the exposure of a patient toradiation and for controlling a radiation source comprising: a radiationsource, a retroreflective element to be mounted closely adjacent thepertinent portion of the patient''s body to be exposed to saidradiation, a light source for directing a beam of light upon theretroreflective element, said light beam being reflected by saidelement, photoresponsive means for receiving the reflected light beamfrom said retroreflective element to develop a signal indicative of anysubstantial change in the position of the patient from a first position,and means connected between said photoresponsive means and saidradiation source and operative to deactivate said radiation source inresponse to a change in the signal from said photoresponsive means. 15.A method of sensing medically significant changes in the position of apatient during a medical radiant energy exposure procedure, comprisingthe steps of mounting a retroreflective element adjacent the patient''sbody, remotely directing a beam of light upon the retroreflectiveelement, and remotely directing the resulting reflected light beam fromthe retroreflective element.
 16. A method according to claim 15,comprising the further step of performing a control function in responseto a change in the reflected light beam.
 17. A method according to claim15, comprising the further step of producing a warning signal inresponse to a change in the reflected light beam.
 18. A method accordingto claim 15, comprising the further step of discontinuing the medicalprocedure in response to a change in the reflected light beam.
 19. Amethod of responding to a medically significant change of position of apatient during a medical procedure comprising the steps of providing aretroreflective element in a fixed relation adjacent the pertinentportion of the pateint''s body, directing a beam of light from a remoteposition toward the retroreflective element, remotely detecting thereflected beam of light from said retroreflective element, producing awarning signal in response to a medically significant change of positionof the patient from a first position to another position, anddiscontinuing the medical procedure in response to said warning signal.20. A method according to claim 19, comprising the further steps ofbeaming radiant energy toward the patient, and discontinuing saidbeaming in response to the signal.
 21. A method according to claim 20 inwhich the retro-reflective element is mounted on the patient.